Non melanoma skin cancer is the most common form of human malignancy accounting for almost 1/3 of all new cancers diagnosed annually in the United States. Murine skin carcinogenesis is a multistage phenomenon and is the most appropriate model for the human non-melanoma skin cancer, at least for squamous cell carcinoma. The identification and characterization of differentially expressed genes in murine skin tumors will help to better understand the pathophysiology and the mechanism of epithelial carcinogenesis. We used the technique of differential display of mRNAs by PCR to identify and clone differentially expressed mRNA transcripts from 7,12-dimethylbenz (a) anthracene -initiated and 12-0- tetradecanoylphorbol-13-acetate promoted papillomas induced on SENCAR mouse skin. We have isolated and partially sequenced 3 novel cDNA clones. Northern analysis and hybridization with amplified total cDNA confirmed the differential expression of these transcripts in tumors. A search of GenBank and EMBL DNA databases revealed that these clones have no homology to catalogued murine sequences. The specific objectives of this proposal are to (1) clone and characterize the full length cDNA molecules of the newly identified differentially expressed transcripts and to determine the complete nucleotide sequence; and (2) to study the kinetics of expression of the newly isolated and cloned cDNAs during the course of skin tumor induction in tumor initiation and tumor promotion protocol. These objectives will be accomplished by (a) constructing a representative cDNA library using purified mRNA from murine skin tumors and by screening this library with isolated cDNA fragments. Strongly hybridizing clones will be isolated and the size of the cloned fragment will be determined by the standard methods; (b) clones with full length inserts will be sequenced completely and the sequences will be compared with the catalogued sequences in the databases; and (c) we will use PCR to study the kinetics of expression of the isolated novel cDNAs in skin following treatment with tumor initiator and promoter at various stages of tumorigenesis protocol. The broad long term goal of these studies is to provide a framework for better understanding the multistage carcinogenesis and devising strategies for its prevention and treatment.